In the early years of this century, electric vehicles were a worthy candidate for city transportation. Their quiet elegance compared favorably to the hand-cranking, noisy and temperamental nature of their rivals powered by the internal combustion engine. Today, however,while considerable effort has been directed to the development of cost-effective, high energy density, power sources for electric vehicles, their ability to compete with the refined, powerful and protean internal combustion vehicles which now meet our needs remains limited at best. The driving range offered by a tankful of gasoline is significant, even when providing power for heat, air-conditioning and other comforts of the modern vehicle (e.g. stereo, telephone, etc.). Despite the environmental advantages offered by electric vehicles, their limited driving range and relatively high cost remain an impediment to their acceptance.
Environmental concerns are becoming paramount in various jurisdictions. Accordingly, there is a continuing effort to develop electric vehicles which will meet or surpass the rigorous environmental standards which are being set, with a convenience for the user which matches that of vehicles powered by internal combustion engines.
A considerable amount of this effort has been devoted to vehicles which are powered by batteries. In this regard, a useful summary on costs, driving range and other considerations is provided in a paper by Ronald Doctors of GMI Inc, Santa Barbara, Calif., entitled "A Systems Approach To Battery Powered Vehicles". Here, it is indicated that factors such as battery weight, battery cost, limited driving range, recharging and other battery maintenance needs, can be a serious deterrent to acceptance by the driving public. These disadvantages are noted with respect to conventional electric vehicles where the battery is intended to stay in the vehicle as an integral part. The need for battery maintenance leads to prolonged periods during which a vehicle is unserviceable.
To lessen the problem, Doctors proposes a system using battery modules which are smaller than integrated batteries, but which allow discharged modules to be quickly exchanged for freshly charged modules merely by driving into a battery exchange center. The exchange centers are staffed and equipped to handle battery recharge and maintenance in an expert manner thus relieving the vehicle owner of such concerns.
The proposal by Doctors has merit. However, it represents a partial solution at best. The driving range with the relatively small modular batteries which he proposes is limited. Accordingly, battery exchange would be required at frequent intervals. In an example which he gives for the California driver averaging about 40 miles per day, battery exchange would be required daily. On the basis that the exchange would take only 30 seconds, he does not see this as a problem. However, 30 seconds surely ignores the amount of time that it takes to drive to and from an exchange center. Further, the repeated installation and removal of batteries, even in a modular form, will attract maintenance, safety and other operational problems of their own. A battery exchange center may provide excellent servicing for battery modules, but the modules, their corresponding receptacles in the vehicles, and electrical interconnections between the modules and the receptacles (the latter of which may be serviced infrequently or sporadically) will be at increased risk of abuse, damage or deterioration with repeated battery exchange.
Battery exchange centers with a degree of automation have been proposed by others: see for example U.S. Pat. No. 4,343,533 (Hane) granted on Aug. 3, 1982 and U.S. Pat. No. 5,549,443 (Hammerslag) granted on Aug. 27, 1996. However, the utility of such centers appears to depend upon standardization in the positioning of batteries or battery modules within the vehicles and in the means of access and egress for the purpose of installation and removal. Further, the utility of such centers may depend upon elaborate systems for the handling of batteries or battery modules once they have been removed: see also U.S. Pat. No. 4,334,819 (Hammerslag) granted on Jun. 15, 1982, and U.S. Pat. No. 4,450,400 (Gwyn) granted on May 22, 1984.